During the construction of the transcontinental railroad through Donner Pass in the 1860s, four tunnels (including a 1,659-foot one), several miles of snowsheds, and two "Chinese Walls" were built by Chinese laborers to lay the lines across Donner Summit. It was by far the most difficult challenge of the entire Sacramento to Ogden Central Pacific Railroad route. Today, these tunnels and snowsheds can be explored by visitors. They are located along Donner Pass Road, west of Donner Lake.